There are 2 reasons why an item may not show on your menu:
The Item is not Available
Make sure that the item is marked as Available in the dashboard
The item has not been added to a Category that's on the menu
In order for an item to appear on the website, it has to be listed within a Category that is currently on the menu
Please note that once the menu is edited, the changes are made immediately. If you don't see the updates on your website right away, try using a private browsing window or clear your cookies & cache prior to visiting the page.